Tumblr - A feature rich and free blog hosting platform offering professional and fully customizable templates, bookmarklets, photos, mobile apps, and social network integration.
PenPal World - Connect with people all over the world
Soup.io - Soup is a tumblelog, a super-easy blog that can do more than just text: post links, quotes, videos...
InterPals - InterPals is a friendly community of over 5 million friends, language learners, travelers and penpals.
Postly - Turn your photos into REAL beautiful postcards. Available on iPhone, iPad and Android. Make friends and family smile with a postcard!
Polyglot Club - Polyglot Club is a new social network for language learners.